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Biomedical subjects

Jay W Calvert

Publications and source records attributed to Jay W Calvert.

13 recordsLinked to original sources
PubMed2006

Adhesion of mesenchymal stem cells to polymer scaffolds occurs via distinct ECM ligands and controls their osteogenic differentiation.

The osteogenic potential of mesenchymal stem cells (MSCs) cultured on poly(lactide-co-glycolide) (PLGA) or poly(caprolactone) (PCL), two widely used polymeric biomaterials that have been reported to differentially support osteogenic differentiation, was compared in these studies. Here we report that MSCs cultured in 3-D PLGA scaffolds for up to 5 weeks significantly upregulate osteocalcin gene expression levels. By contrast, osteocalcin expression was markedly downregulated in 3-D PCL-based constructs over the same time course. We hypothesized that differential adsorption of extracellular matrix (ECM) proteins present in serum-containing culture medium and subsequent differences in integrin-mediated adhesion are responsible for these differences, and tested this hypothesis using thin (2-D) polymeric films. Supporting this hypothesis, significant amounts of fibronectin and vitronectin deposited onto both materials in serum-containing osteogenic media, with type-I collagen present in lower amounts. Adhesion-blocking studies revealed that MSCs adhere to PCL primarily via vitronectin, while type-I collagen mediates their attachment to PLGA. These adhesive mechanisms correlated with higher levels of alkaline phosphatase (ALP) activity after 2 weeks of monolayer culture on PLGA versus PCL. These data suggest that the initial adhesion of MSCs to PLGA via type-I collagen fosters osteogenesis while adhesion to PCL via vitronectin does not, and stress the need for an improved molecular understanding of cell-ECM interactions in stem cell-based therapies.

Cell Adhesion↗
PubMed2006

Free flap reconstruction for infection of ankle fracture hardware: case report and review of the literature.

BACKGROUND: Clinical management of orthopedic hardware infections related to ankle fracture fixation may present difficult therapeutic dilemmas. Typically, management includes removal of the hardware, debridement of necrotic tissue, and eventual placement of an alternative method of stabilization, usually, an external fixator or cast. However, problems arise when the fracture cannot be managed adequately with an external method. Such is the case with supination external rotation (SER) fractures, yet maintaining the hardware in the setting of infection typically is not considered an option. METHODS: Case report and review of pertinent English-language literature. RESULTS: The patient was a 47-year-old man with diabetes mellitus who sustained a type IV SER fracture that was treated with plate and screw fixation. Six weeks postoperatively, he presented with infection of the lateral ankle incision and the hardware. This was treated with debridement of the wound and dressing changes while leaving the hardware in place. It was decided to use a free muscle flap in an effort to preserve the ankle for a functional outcome versus the alternative of a below-knee amputation. With a free rectus abdominis flap, the lower extremity was preserved, and after four months, the patient was able to walk. One year postoperatively, the patient was ambulating without difficulty, and the hardware was still in place. CONCLUSIONS: This report examines the dilemma of SER ankle fractures and how management strategies must be tailored to the individual situation. In some cases, the hardware must be considered essential to avoid below-knee amputation.

Ankle Injuries↗
PubMed2006

Survival of diced cartilage grafts: an experimental study.

BACKGROUND: Use of diced cartilage grafts in rhinoplasty surgery has recently undergone a dramatic resurgence. Some authors recommend wrapping diced cartilage with oxidized methylcellulose (i.e., Surgicel). Others prefer wrapping diced cartilage with autogenous deep temporal fascia. This study was designed to compare the behavior of diced cartilage grafts as an isolated entity or when wrapped with either Surgicel or deep temporal fascia. METHODS: Septal cartilage and deep temporal fascia were obtained from five patients in this institutional review board-approved study. The cartilage was diced into 0.5-mm pieces and implanted into subcutaneous dorsal skin pockets of Rowlett nude rats as isolated diced cartilage grafts, or wrapped in Surgicel or deep temporal fascia. Pieces of Surgicel and fascia were implanted alone as controls. The specimens were harvested at 8 weeks; processed by thin-section histology; stained with hematoxylin and eosin, Masson's trichrome, glial fibrillary acidic protein, safranin-O, and Evans van Gieson; and evaluated to determine cartilage viability and architectural characteristics. RESULTS: Diced cartilage wrapped in Surgicel yielded the lowest percentage viability and minimal staining with hematoxylin and eosin, trichrome tissue, safranin-O, and Evans van Gieson stains. Diced cartilage grafts wrapped in fascia had the greatest percentage of viable cartilage. The grafts wrapped in deep temporal fascia also demonstrated the strongest staining with the aforementioned stains. Differences in uptake of glial fibrillary acidic protein were not noticeable between the three groups. However, absolute numbers of nucleated lacunae and basophilic lacunae were significantly higher for grafts wrapped in deep temporal fascia. CONCLUSIONS: Diced cartilage grafts have reemerged as a viable method for nasal reconstruction in both primary and secondary rhinoplasty. Wrapping diced cartilage specimens contains the individual pieces and facilitates graft placement. Surgicel wraps appear to incite an inflammatory response and subsequent absorption of the cartilage. Fascia wraps appear to minimize inflammatory responses to the cartilage, thereby preserving healthy cartilage. This study demonstrates that deep temporal fascia is the preferred envelope with which to facilitate graft containment and maintain chondrocyte viability of diced cartilage grafts.

Animals↗
PubMed2006

The evolution of the midface lift in aesthetic plastic surgery.

The midface lift has recently gained significant popularity with many surgeons. It allows the surgeon an opportunity to achieve greater facial harmony with facial rejuvenation procedures by correcting midfacial atrophy, addressing the tear trough deformity, and correcting the perceived malposition of the malar fat pad. This article examines the history of midfacial procedures. Surgical attempts at improving the aging face have evolved from minimal excisions and skin closure to aggressive dissections at multiple planes. The midface target area is peripheral to classic approaches, and its correction has required further anterior dissection from a distance or direct access centrally. Ultimately, conquering the stigmata of midface aging is entirely related to vectors and volume.

Aging↗
PubMed2006

Histological analysis of human diced cartilage grafts.

BACKGROUND: Grafting the radix and dorsum of the nose has been controversial and the plastic surgery community has recently revisited diced cartilage grafts. Previous articles by the authors reported clinical failures of diced cartilage-Surgicel-wrapped grafts and the successful implementation of diced cartilage-fascia-wrapped grafts for rhinoplasty procedures. This article investigates four means of radix and dorsum augmentation, including banked and fresh septum. METHODS: Twenty-seven human specimens were taken from rhinoplasty patients: six failed diced cartilage-Surgicel-wrapped grafts, eight diced cartilage-fascia-wrapped grafts, and 13 specimens of fresh cartilage or previously placed cartilage grafts. All were stained with hematoxylin and eosin, Masson's trichrome, safranin-O, glial fibrillary acidic protein, and Evans' van Gieson stains and analyzed for chondrocyte viability, matrix proteins, and regenerative potential of the cartilage. RESULTS: The diced cartilage-Surgicel-wrapped grafts showed disorganized fibrosis, loss of nuclei in chondrocyte lacunae, and negative glial fibrillary acidic protein staining. All specimens contained remnants of Surgicel and evidence of foreign body reaction. The diced cartilage-fascia-wrapped grafts showed normal histologic characteristics, healthy cartilage pieces with viable chondrocytes in their lacunae, positive glial fibrillary acidic protein staining, and organized capsule of fibrosis surrounding the cartilage pieces. The fascia was viable and showed an organized architecture distinctly different from the disorganized scar tissue of the diced cartilage-Surgicel-wrapped grafts. CONCLUSIONS: Given the histologic findings, diced cartilage-Surgicel-wrapped grafts absorbed due to foreign body reaction. Diced cartilage-fascia wrapped grafts survived and demonstrated normal cartilage viability. According to the clinical performance and analysis of these grafts, diced cartilage-fascia is the most reliable way to augment the nasal dorsum and radix with autologous diced cartilage.

Cartilage↗
PubMed2005

Nerve growth factor expression response to induction agent booster dosing in transfected human embryonic kidney cells.

To assess whether nerve growth factor (NGF) expression would respond to booster dosing with the inducing agent ponasterone A, human embryonic kidney cells (HEK-293) were transfected with human NGF cDNA. Cells were cultured for 5 days in media with or without ponasterone A. On day 5, controls received a ponasterone A media replacement, whereas experimental groups received ponasterone A booster media replacement. NGF protein expression bioactivity was assessed using a PC-12 cell bioassay and the concentration of secreted NGF was quantified using NGF enzyme-linked immunosorbent assay. Cells with and without ponasterone A were left for 5 days without changing the medium. On day 5, the supernatants were collected and flash-frozen for enzyme-linked immunosorbent assay. The ponasterone A-positive and -negative booster medium was replaced in the appropriate wells. Supernatants were collected from the wells at 2, 4, and 6 days after the booster dose and removal of original supernatant. The medium was flash-frozen for enzyme-linked immunosorbent assay (1.5 ml), and the remaining 500 mul was transferred to PC-12 cells seeded onto 12-well plates to determine NGF bioactivity. All experiments were performed in quadruplicate. NGF production was measured daily by enzyme-linked immunosorbent assay over a 6-day period after the ponasterone A booster to a maximal release of 1233 +/- 130 pg/ml at day 6 (11 days after original induction). Maximal NGF production per 10(3) cells was 2.5 +/- 0.61 pg at day 6. Bioactivity was determined by percentage differentiation (per 100 cells counted) at 26, 52, and 98 percent for ponasterone A-treated wells on 2, 4, and 6 days after booster dosing (7, 9, and 11 days after induction), respectively. PC-12 cell differentiation was not visualized in the ponasterone A-negative control wells. Human NGF-EcR-293 cells can inducibly secrete bioactive NGF when exposed to the induction agent ponasterone A. Furthermore, repeated bioactive NGF expression peaks beyond that previously demonstrated can be achieved using induction agent booster dosing, indicating the ability to regulate the system over an extended period.

Cell Differentiation↗
PubMed2005

Osteoblastic phenotype expression of MC3T3-E1 cells cultured on polymer surfaces.

BACKGROUND: Current efforts in bone tissue engineering have as one focus the search for a scaffold material that will support osteoblast proliferation, matrix mineralization, and, ultimately, bone formation. The goal is to develop a bone substitute that is functionally equivalent to autograft bone. Previously published reports have shown that osteoblasts exhibit varying rates and degrees of proliferation and mineralization when grown on different surfaces. METHODS: This study presents a histologic and biomolecular analysis of MC3T3-E1 murine preosteoblast cells grown on poly(lactide-co-glycolide) (PLGA) versus poly(-caprolactone) (PCL), two commonly studied scaffold polymers. MC3T3-E1 cells were cultured on slides coated with either PLGA or PCL, and on uncoated glass slides as control, with six slides in each group. After 6 weeks in culture, the cells were stained for osteocalcin, alkaline phosphatase activity, and matrix mineralization. In addition, to assess the effects of the surface material on phenotypic expression at the molecular level, MC3T3-E1 cells were cultured on polymer-coated 24-well plates for 4 days, and analyzed by reverse transcription polymerase chain reaction for the expression of osteocalcin and alkaline phosphatase. RESULTS: The results showed that three groups of slides stained positively for osteocalcin at 6 weeks. However, markedly less alkaline phosphatase activity and mineralization were observed on the cells grown on PCL. Real-time polymerase chain reaction assays subsequently revealed decreased expression of both markers by cells cultured on PCL compared with PLGA. CONCLUSIONS: These results suggest that PCL does not support the full expression of an osteoblastic phenotype by MC3T3-E1 cells. PCL, therefore, is less desirable as a scaffold polymer in bone tissue engineering in so far as supporting bone formation is concerned. However, because PCL has favorable handling characteristics and strength, modifications of PCL may prompt further investigation.

3T3 Cells↗
PubMed2004

Pharmacologic enhancement of rat skin flap survival with topical oleic acid.

This study was instituted to investigate in a rat model the effect of topical coadministration of the penetration enhancer oleic acid (10% by volume) and RIMSO-50 (medical grade dimethyl sulfoxide, 50% by volume) on rat skin flap survival. A rectangular abdominal skin flap (2.5 x 3 cm) was surgically elevated over the left abdomen in 40 nude rats. The vein of the flap's neurovascular pedicle was occluded by placement of a microvascular clip, and the flap was resutured with 4-0 Prolene to its adjacent skin. At the end of 8 hours, the distal edge of the flap was reincised to gain access to the clips and the clips were removed. After resuturing of the flap's distal edge to its adjacent skin, the 40 flaps were randomly divided into four groups. Group 1 (control) flaps were treated with 5 g of saline, group 2 (dimethyl sulfoxide) flaps were treated with 2.7 g of dimethyl sulfoxide (50% by volume), group 3 flaps (oleic acid) were topically treated with 0.45 g of oleic acid (10% by volume), and group 4 (dimethyl sulfoxide plus oleic acid) flaps were treated with a mixture of 0.45 g of oleic acid (10% by volume) and 2.7 g of dimethyl sulfoxide (50% by volume) diluted in saline. Each flap was topically treated with 5 ml of drug-soaked gauze for 1 hour immediately after clip removal to attenuate reperfusion injury. Thereafter, drug was applied topically once daily for 4 more days. Digital photographs of each flap were then taken on day 6 and the flaps were then harvested. The percentage of skin survival in each flap was determined by computerized morphometry and planimetry. The mean surviving area of group 3 (oleic acid-treated flaps) was 23.60 +/- 4.19 percent and was statistically higher than that in group 1 (control, saline-treated flaps) at 7.20 +/- 2.56 percent. The mean surviving area of group 2 (dimethyl sulfoxide-treated flaps) at 18.00 +/- 5.23 percent and group 4 (oleic acid- and dimethyl sulfoxide-treated flaps) at 9.90 +/- 3.44 percent did not achieve statistically higher mean surviving areas than controls. A topical solution of oleic acid (10% by volume) caused a statistically significant increase in the survival of rat abdominal skin flaps relative to controls. Dimethyl sulfoxide and the two experimental drugs together did not increase the percentage of flap survival when given as a single 5-ml dose released from a surgical sponge at reperfusion for 1 hour and then daily for a total of 5 days. The reasons for the lack of response are unknown but may have included the technical difficulty of delivering an adequate dose of dimethyl sulfoxide topically and immiscibility between dimethyl sulfoxide and oleic acid. Further studies may be warranted.

Abdomen↗
PubMed2004

Diced cartilage grafts in rhinoplasty surgery.

The use of diced cartilage grafts in rhinoplasty surgery was recently revived by Erol with the publication of his technique for "Turkish delight" grafts (i.e., diced cartilage grafts wrapped in Surgicel). The present study details the authors' experience with 50 consecutive diced cartilage grafts used in three configurations during a prospective study of 50 primary and secondary aesthetic rhinoplasty procedures performed by the senior author (Daniel). Part I consists of 22 diced cartilage grafts wrapped in Surgicel and placed in the radix (n = 14), radix/upper dorsum (n = 4), and full-length dorsum (n = 4). All grafts were performed adhering meticulously to Erol's technique without modification. This portion of the study was halted abruptly at 4 months because of the unexpected absorption and clinical failure of all diced cartilage grafts wrapped in Surgicel. Subsequently, five patients had revision surgery, and biopsy specimens were taken at the prior grafting site and analyzed histologically. After this clinical failure, part II of the study began, consisting of 20 patients who had diced cartilage grafts wrapped in fascia. The range of applications was comparable: radix (n = 12), radix/dorsum (n = 3), and full-length dorsum (n = 5). Because of our prior practice of overcorrecting by 20 percent with diced cartilage grafts wrapped in Surgicel, we had excessive amounts of material in six of our initial diced cartilage wrapped in fascia radix grafts, but no subsequent grafts. The overcorrections were easily reduced at 6 weeks to 11 months postoperatively using a pituitary rongeur under local anesthesia, and the material was sent for histologic analysis. Minimum 1-year follow-up of all 20 cases has shown maintenance of the grafts without evidence of absorption. Part III of this study comprised eight patients who had diced cartilage grafts without a fascial covering placed throughout the nose, including on the sides of osseocartilaginous rib grafts to the dorsum. At 14 months, there was no evidence that any of these grafts had been absorbed. Histologic analysis of the biopsy specimens from the diced cartilage grafts wrapped in Surgicel showed evidence of fibrosis and lymphocytic infiltrates with small amounts of Surgicel visible on birefringent microscopy. Remnants of cartilage were present but were metabolically inactive on the basis of negative glial fibrillary acidic protein staining. Control specimens of fresh septal cartilage and banked septal cartilage were remarkably similar to each other and demonstrated normal cartilage architecture and cellular activity. The diced cartilage grafts wrapped in fascia showed coalescence of the diced cartilage into a single cartilage mass, with viable cartilage cells and normal metabolic activity on the basis of glial fibrillary acidic protein staining. All of the diced cartilage grafts wrapped in Surgicel absorbed and failed to correct the clinical problem for which they were performed. All of the diced cartilage grafts wrapped in fascia and pure diced cartilage grafts did correct the clinical deformities and appear to have survived completely. The diced cartilage grafts wrapped in fascia placed along the dorsum were distinctly palpable throughout the postoperative period, as was one prior case with a 6-year follow-up. The authors' clinical experience confirms the experimental studies of Yilmaz et al. that question the use of Surgicel for wrapping diced cartilage grafts in clinical rhinoplasty surgery.

Absorption↗
PubMed2004

Mandibular reconstruction: are two flaps better than one?

This study compared the combined iliac and ulnar forearm flaps with the osteomusculocutaneous fibular free flap for mandibular reconstruction. A retrospective study of 40 patients who had oromandibular reconstruction was performed, of whom 23 patients had a combined iliac crest without skin and ulnar forearm free flap. Seventeen patients had an osteomusculocutaneous free fibular flap. Ten women and 30 men with a mean age of 57.5 years comprised this study population. Ninety percent of the cases were squamous cell carcinoma (55%, T4), of which 11% were recurrent tumors. Anterolateral mandibular defects constituted 52.9% of the fibular reconstructions and 60.9% accounted for the iliac/ulnar reconstructions. The mean bone gaps were 8.79 cm and 8.95 cm respectively. Functional evaluation was based on the University of Washington Questionnaire through phone calls and personal communication. The mean hospital stay was 15.43 days and 10.09 days for the fibular and iliac/ulnar flaps respectively. The facial artery (64.7%) and facial vein (60%) were the main recipient vessels for the fibular reconstructions whereas the external carotid artery (95.6%) and the internal jugular vein (66.7%) were the main recipient vessels for the iliac/ulnar reconstruction. Overall flap survival was 96.8% (100% of fibular flaps and 95.65% of iliac/ulnar flaps). Two flaps were lost in the iliac/ulnar series because of unsalvageable venous thrombosis. Local complications for the iliac/ulnar flaps were 30.4% but were 5.9% for the fibular reconstructions. Function such as speech, swallowing, and chewing were notably better in the fibular than the iliac/ulnar group in 23 of the patients tested. The cosmetic acceptance of 77.8% of the fibular flaps was judged to be excellent and good, whereas 71.4% of the iliac/ulnar flaps were rated good. It appears that within this study population the free osteomusculocutaneous fibular flap had fewer local complications and a higher flap survival rate than the combined iliac/ulnar forearm flaps. Overall functional outcome was also improved. The use of the double flap may be appropriate in massive oromandibular defects, but may be less appropriate in more modest functional reconstructions of mandibular defects.

Adult↗
PubMed2003

New frontiers in bone tissue engineering.

No single scientific field can generate the ideal method of engineering bone. However, through collaboration and expansion of programs in bone tissue engineering, the right combination of materials, cells, growth factors, and methodology will come together for each clinical situation such that harvesting bone grafts will become obsolete. This article reviews the need for engineered bone and provides a historical perspective of bone engineering research, current research efforts, and the future direction of this work.

Biocompatible Materials↗
PubMedDate not supplied

Diffusion limits of an in vitro thick prevascularized tissue.

Although tissue engineering promises to replace or restore lost function to nearly every tissue in the body, successful applications are currently limited to tissue less than 2 mm in thickness. in vivo capillary networks deliver oxygen and nutrients to thicker (> 2 mm) tissues, suggesting that introduction of a preformed in vitro vascular network may be a useful strategy for engineered tissues. This article describes a system for generating capillary-like networks within a thick fibrin matrix. Human umbilical vein endothelial cells, growing on the surface of microcarrier beads, were embedded in fibrin gels a known distance (Delta = 1.8-4.5 mm) from a monolayer of human dermal fibroblasts. The distance of the growth medium, which contained vascular endothelial growth factor and basic fibroblast growth factor, from the beads, C, was varied from 2.7 to 7.2 mm. Capillaries with visible lumens sprouted in 2-3 days, reaching lengths that exceeded 500 microm within 6-8 days. On day 7, capillary network formation was largely independent of C; however, a strong inverse correlation with Delta was observed, with the maximum network formation at Delta = 1.8 mm. Surprisingly, the thickness of the gel was not a limiting factor for oxygen diffusion as these tissue constructs retained a relatively high oxygen tension of > 125 mmHg. We conclude that diffusion of oxygen in vitro is not limiting, allowing the development of tissue constructs on the order of centimeters in thickness. In addition, diffusion of fibroblast-derived soluble mediators is necessary for stable capillary formation, but is significantly impeded relative to that of nutrients present in the medium.

Capillaries↗